Achieving service parity between IPv4 and IPv6 performance will be a critical challenge to service providers. In theory, telecom IPv6 performance should equal IPv4 performance. In practice, IPv6 service parity is more complicated than enabling the next-generation Internet Protocol on routers.

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If we do our jobs right as providers of Internet connectivity, we should be delivering you IPv6 seamlessly without it ... being secondary [to] or not as efficient as v4.

Martin Levy Director of IPv6 Strategy, Hurricane Electric

Subscribers may notice the performance of their favorite websites or services lagging if the traffic must pass through gateways to use transition technologies or if homegrown applications are ill-equipped to support IPv6's 128-bit addressing scheme. If telecom network monitoring tools aren't capturing IPv6 traffic and alerting telecom engineers to problems, they will have to rely on customer complaints to prompt remediation.

"If we do our jobs right as providers of Internet connectivity, we should be delivering you IPv6 seamlessly without it even being open for question -- without it being secondary [to] or not as efficient as v4," said Martin Levy, director of IPv6 strategy at Hurricane Electric, which claims to operate the world's largest IPv6-native Internet backbone. "We've wanted everything to be equal and we got to that point, [but that] was, I must say, nontrivial to be honest."

IPv6 performance, service parity: Years of lab experience and trials could pay off

Hurricane Electric recently deployed Brocade's NetIron XMR Internet backbone routers and MLXe core routers to natively support IPv4 and IPv6 traffic at up to 100 Gbps. Prior to its first deployment with Foundry Networks four years ago -- before Brocade acquired it -- Hurricane Electric's previous vendor's IPv6 support was "not able to deliver production quality dual-stack v6 services" and "very subservient to v4" support, Levy said, declining to name the vendor publicly.

The upgrade is the latest in Hurricane Electric's decade-long efforts to optimize IPv6 performance and ensure service parity, Levy said.

"We have a pretty mature -- as do most people -- v4 environment. It's highly commercial, moving large amounts of data, has a significant amount of interconnect, customer growth, etc.," he said. "But what we didn't have was the same for v6. That's what we were after. That was the point of everything. To make sure we could run v6 on par -- not to be substandard, not to be an afterthought, but to be an absolute on-par offering with our standard v4 offering."

Using NAT to run millions of IPv4 set-top boxes on IPv6 video servers

Brocade recently announced IPv6 performance-related updates to the software on its application delivery controllers (ADCs), the ServerIron ADX series, which includes a carrier-class appliance. The latest version of the software enables the ADXs to function as network address translation (NAT) gateways using the NAT64 standard.

The NAT64 standard has enabled the controllers to manipulate Layer 7 elements. Legacy gateways based on NAT444, also known as large-scale NAT, are unable to achieve this Layer 7 fluency because they cannot work above Layer 3, said Keith Stewart, director of product management at Brocade.

A large cable and Internet service provider, which Stewart declined to name, recently struggled to provide video on-demand services from its IPv6-only servers to tens of millions of legacy IPv4-only set-top boxes. Upgrading every single customer's set-top box to a new IPv6-capable one would have been too expensive, so it needed a gateway to mediate, Stewart said.

The cable provider also wanted to change its distribution model to something more distributed, but it had to replicate service delivery infrastructure in every one of its markets because it reused IP addresses for its set-top boxes in different routing domains.

The provider recently deployed the ADXs to serve not only as gateways between the Video on Demand servers and customer-premise hardware, but also as a way to dupe the routers into recognizing the duplicated set-top box addresses as unique, Stewart said. Using its Layer 7 capabilities, the controller inserted 96-bit prefixes in the legacy 32-bit IPv4 addresses to make them look like 128-bit IPv6 addresses to the routers; the prefixes designated the geographic market.

A gateway using NAT444 could not have achieved that "pseudo addressing," Stewart said. Even without the addressing issue, NAT444 performs translation slower than NAT64 and would knock IPv6 performance, he added.

Comcast Corp, which began testing IPv6 on its live network in January 2010, has made IPv6 performance and service parity "a guiding light throughout the duration of the program so far," said John Jason Brzozowski, chief IPv6 architect and distinguished engineer at Comcast.

Engineers in Comcast Innovation Labs have worked with the protocol for years. The service provider recently launched a trial in Littleton, Colo., testing IPv6 in a native dual-stack configuration over DOCSIS 3.0, and it has also begun evaluating IPv6 support for set-top boxes, Brzozowski said. Comcast publicly announced last month that it would abandon its trials with a tunneling technology known as "IPv6 rapid deployment," or 6rd. The decision was made in favor of pursuing native IPv6 support network-wide, which yields a "more advanced and highly-capable" level of service, Brzozowski said.

"The technology trials ... play a very big role in our ability to learn how to make the introduction of v6 seamless to our subscribers," he said. "[IPv6 performance] has always been a very high priority for us to make sure that we maintain parity as best we can."

"It must be built into the early phases or you'll start losing your customers," he said. "The moment you enable IPv6 in your network, your customers will use IPv6 preferentially to connect to servers with IPv4 and IPv6 addresses. If IPv6 doesn't work as well as IPv4, you'll directly hurt customers."

Realistically, however, most service providers have only begun to pilot IPv6 on their networks to get operational experience with it, Pepelnjak said.

Service providers and IPv6 experts have repeatedly acknowledged in interviews with SearchTelecom.com over the past year that vendor support for IPv6 is improving, but it remains inconsistent at best.

"Vendors [haven't come] to the marketplace very aggressively to offer anything in the v6 space. In fact, very far from it -- it was like pulling teeth to get vendors to deliver anything in terms of v6 capability," Levy said. "We have been pushing for the last umpteen years [for them] to build solutions that are on-par, meaning anything I can do with IPv4, I should be able to do with IPv6."

Those shortcomings over the years have ranged from the trivial to the complex. Vendors have been slow to meet simple demands such as having packets move at the same speeds for both protocols. They also struggle to support more nuanced areas of back-end infrastructure, such as having network monitoring flow capabilities be available in IPv6, Levy said.

Comcast was more forgiving of its vendors but acknowledged that limitations for IPv6 feature parity remained a challenge.

"That's not something I can elaborate deeply on, but I can tell you there's a lot of progress and great work people are doing in the v6 space," Brzozowski said. "But there's still work to be done."

At least with what is IPv6-capable, service providers are likely to find that homegrown back-end systems will require the most attention and "some hardware-based platforms have very low default limits for IPv6 routing tables," according to Pepelnjak.

Many telecom network equipment vendors "still lack feature parity" between IPv6 and IPv4 products, Pepelnjak said. Shortcomings include missing security features and the ability to support small customer multi-homing.

John Curran, president and CEO of the American Registry for Internet Numbers (ARIN), said the onus for IPv6 performance isn't entirely on telecom network equipment vendors and service providers. Content providers that fail to enable IPv6 support on their Web servers and force visitors to take a performance hit passing through gateways risk revenue losses, he said.

"I expect the service providers will be very clear in telling [subscribers when] the website they're going to is only on IPv4 and the consequence of it," Curran said.

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